Powdery Mildew Resistance in Barley Landraces from Morocco

Nineteen barley landraces collected from Morocco were screened for resistance to powdery mildew[ The landraces originated from the collection at the Polish Gene BankIHAR Radziko w\ Poland[ The _fteen landraces tested showed powdery mildew resistance reactions and 24 sin! gle plant lines were selected[ Twenty!one of these lines were tested in the seedling stage with 29\ four lines with 06 and another 09 lines with 12 di}erential isolates of powdery mildew\ respectively[ The isolates were chosen according to their virulence spectra observed on the Pallas isolines di}erential set[ Nine lines "E 0918!0!0E0931!1!1\ E0949!0!0\ E 0943!4!0\ E0945!1!4\ E0945! 2!0\ E0950!0!0\ E0950!0!2 and E0956!0!1# which orig! inated from seven landraces showed resistance to all prevalent European powdery mildew virulence genes[ The most frequent score was 1 and 05 lines showed this reaction for inoculation with most isolates used[ The distribution of reaction type indicated that about 66) of all reaction types observed were classi_ed as powdery mildew resistance "scores 9\ 0 and 1#[ In all lines the presence of unknown genes alone or in combinations with speci_c ones was postulated[ Four di}erent resist! ance alleles "Mlat\ Mla5\ Mla03 and Mla01# were pos! tulated to be present in 09 tested lines alone or in combination[ Alleles Mlat\ Mla5 and Mla03 were pos! tulated to be present in four and Mla01 in two tested lines\ respectively[ The value of barley landraces for diver! si_cation of resistance genes for powdery mildew is dis! cussed[